The invention is related to a compensating coupler using a spring drive to connect a rotary (reciprocating) input drive to a rotary (reciprocating) output drive. The coupler exhibits very low backlash and compensates for misalignment between the input and output drives.
It is known to provide couplings between a rotary or reciprocating input shaft to an output shaft wherein the output shaft makes a corresponding angular movement to that movement of the input shaft.
Such drives have application in valving systems wherein an actuator turns a valve to open and close it while at the same time the actuator or valve drives an indicator or positioner that identifies the position of the valve. These drives are called "selsyn" drives to indicate that angular input is translated to an equal angular output at a remote location from the input.
Problems occur with such drives in that complicated mechanisms have to be provided to align square, octagonal or hexagonal input and output drive shafts. Where round shafts are used, different types of aligning mechanisms are required for the couplings. Usually a nut is screwed on the round shaft or a flat is provided on the rounded surface for attachment to a coupler.
With polygonal drive shafts positive position indication is more easily obtained since an indexed drive from a flat surface of a rotating shaft is easier than from a round surface.
Ideally, the coupling should allow for some axial (X and Y directions) and some rotational misalignment between input and output without sacrificing the quality of the traced movement. At the same time, the coupling should be simple in construction and inexpensively manufactured and assembled. Normally, the fewer the parts in the coupling, the more economic is its manufacture and installation.
It is an object of this invention to provide a coupling that is simple in manufacture, easy to assemble, with a high quality traced movement (low backlash) and which compensates for some misalignment between input and output.
These and other objects are achieved by providing a one-piece coupling having a plurality of legs extending up from a hub for receiving a first drive adjacent the ends of the legs and tabs extending up from the hub for receiving a second drive. A preferred embodiment of such a coupling is obtainable from a spring stock material cut with four legs at 90.degree. intervals about a center hub. The hub includes a square hole with four tabs adjacent thereto. The tabs are cut at a 45.degree. angle with respect to the legs such that the axis of each leg is in alignment with side edges of adjoining tabs. The tabs are bent at an approximate 75.degree. angle with respect to the hub and are straight along their length. The length of the tabs are approximately 1/6 the length of the legs. The legs include a first portion co-planar with and extending to the hub, a middle portion extending from the first portion and curved toward the hub and terminating at a 75.degree. angle from the hub to parallel the tabs and an end portion (approximately 1/6 the length of the leg) bent outwardly approximately 60.degree. from the middle portion of the leg that is parallel to the tab.
A first square drive shaft is inserted into the square hole in the hub from the side away from the tab and leg ends and is held by the inwardly sloped tabs.
A second square drive shaft is inserted from an area adjacent the open end of the legs with flat sides thereof aligned approximately 90.degree. with respect to sides of the first square drive shaft, to rest with its flat sides between the spring legs. If either drive shaft is not square, at least one flat axis surface is required. This can be a nut threaded on a circular shaft or a milled flat.
While the preferred embodiment of the coupling has been shown with four legs and tabs, different numbers could be used. E.g., with hexagonal drives, one could use a six-legged and six-tabbed coupling; for octagonal drives, one would use eight-legged and eight-tabbed coupling, etc. Also the input and the output do not need to have the same number of sides. The number of legs could differ from the number of tabs or alternatively only some of the sides need be grasped between the legs and/or tabs.
Other objects, advantages and moved features of the present invention will become apparent from the following detailed description of the inventions when considered in conjunction with the accompanying drawings.